Patent GB-191229354-A (GB)
Title: Improvements in or relating to Telephone Systems.
Filed: 1912-12-20
Granted: 1913-12-22
Abstract: 29,354. Automatic Telephone Manufacturing Co., [Automatic Electric Co.]. Dec. 20. Semi-automatic exchange systems; metering- systems.-In a system in which calling lines are connected by non-numerical switches to operator's positions, the meter of the calling subscriber is operated when the called subscriber answers. In the system shown in Figs. 1 and 2, this is effected by a reversal of the current on the calling line, and in the system shown in Figs. 3 and 4 by a momentary strengthening of the current through the meter, which is connected in parallel with the cut-off relay of the calling line. Means are provided for preventing the meters being operated more than once for each call. Operators' meters are provided to register the total number of calls and the total number of effective calls over each cord. First arrangement, Figs. 1 and 2. When the subscriber A<1>, Fig. 1, removes his receiver, his line-switch C' operates substantially in the manner described in Specification 1421/10 to extend the call to a secondary line-switch C<5>, which in a similar way extends the connexion to an idle plug cord O, the relay 44 of which is energized by current passing over the contacts of a reversing-relay 45 and through the substation. Control of line-switches and master-switches, Fig. 1. The master-switches D<1>, D<2> operate to control the primary and secondary line-switches in the manner described in Specification 15,072/12, the controlling-relay 87 of switch D' being connected to the usual segment 34, which is connected in turn to the individual contacts a by a wiper 35. In order to prevent a primary line-switch seizing a secondary line-switch, the trunks from which are all in use, relays 81, 81<a>, 81<b>, individual to such trunks, have their contacts connected in series, so that when all such trunks are busy, a relay 105 is energized and grounds the operative windings of all the group of secondary line-switches C<5>, thereby making such switches test busy to the primary masterswitches D<1>. If, when all the trunks from a certain group of secondary line-switches are in use, a subscriber called before the plunger of his line-switch had been picked up by the plunger shaft after a previous call, he would be connected to the same secondary switch as before, but without further result. In order to prevent this, means are provided whereby, when all the trunks from a group of secondary switches are in use, the master-switches of all the primary line-switches, having access to this group of secondary switches, are caused to make a complete oscillation so as to pick up all the idle plungers. This means comprises a set of contacts b, leading to the various masterswitches, a segment 37, and a wiper 38 rotated slowly step-by-step by the magnet 40, and a second magnet 39 controlling a detent so as to maintain the wiper 38 in any advanced position. When the relay 105 is energized as previously described, ground G<9> is connected to the segment 37, to the detent magnet 39, and to a slow-release relay 109 and the magnet 40. The relay 109 energizes a second slow-release relay 110, which in turn disconnects the relay 109, so that the magnet 40 is repeatedly energized and steps the wiper 38 over the contacts b, thereby grounding in succession the controlling-relays 87 of the primary master-switches for a sufficiently long time to enable the plunger shaft to make a complete oscillation and pick up all the idle plungers. The keys K, K<1>, Fig. 1, allow the cord to be made busy should it be desired to take it out of service. Calling and supervisory signals, Fig. 1. The relay 44, energized over the calling line, lights up the lamp 42, the circuit including a normal contact of a relay 91, energized when the calling- plug P, Fig. 2, is inserted. A relay 92, in multiple with the relay 91, lights a lamp 43, which is extinguished when the relay 98 is energized upon the response of the called subscriber. Supply of ringing-current, Fig. 1. The ringing-key 46, held in its depressed position by a relay 47, connects the battery B' and ringing-generator 50 through the interrupters 48, 49, alternately to line. In the first non- ringing interval after the called subscriber replies, the relay 47 is energized by the direct current and releases the key. Metering-arrangements, Fig. 1. During the establishment of the connexion, current flows in opposite directions through the two windings of the meter 52, but when the called subscriber replies, the relay 101 energizes the reversing- relay 45, thus reversing the current in the lefthand winding so as to actuate the meter. In the attracted position of the meter armature the left-hand winding is short-circuited, but the right-hand winding maintains the armature attracted. Release, Fig. 1. When the subscribers hang up, the relays 44, 98 re-establish the circuits of the lamps 42, 43. The withdrawal of the plug de-energizes relays 91, 92, thus removing the ground on the hold-on winding 84 of the lineswitch C<1>, which releases, and opens at contact 16 the holding-circuit of the line-switch C<5>. Second arrangement, Figs. 3 and 4. In this system, the operation of the primary and secondary switches C<3>, C<6> and their masterswitches D<3>, D<4> closely resembles that shown in Figs. 1 and 2, except that the line and cut-off windings are shown as separate relays 53, 54. When the call is extended to the cord O<1>, the relay 117 energizes over the calling line and grounds the holding-circuits of the switches C<3>, C<6>. A circuit through a high-resistance relay 124 is also completed for the meter 56 and cut-off relav 54. Calling and supervisory signals, Fig. 3. The relay 124 closes a circuit for the lamp 127 over a normal contact of the relay 130, which is energized, in multiple with a relay 131, when the calling plug is inserted. The relay 131 closes a circuit over contacts 135, 136 for a slowrelease relay 137, which by closing a contact 140 energizes a relay 142 in series with the lamp 141. When the called subscriber replies, a relay 145 is energized over the called line, and puts a relay 146 in parallel with the lamp 141, thus extinguishing it. Metering arrangements, Fig. 3. In addition to the subscriber's meter 56, operators' cord meters 57,58 are provided, the meter 57 registering effective calls while the meter 58 registers all calls made over the cord. The relay 137, energized as previously explained, on inserting the calling-plug, completes a circuit over contacts 135, 138 for the meter 58, but this circuit is broken after a short-interval owing to the relay 137 being disconnected by the self-locking relay 142. The meter 58 can therefore be only operated once. When the called subscriber replies, the relay 146, energized as described above, excites a slow-release relay 148 over contacts 150, 149, 135. The relay 148 connects a reversely-connected battery B<3> through a relay 156 and contacts 125, 126 to the meter 56, and battery B<2>. These batteries being in series, the current is increased sufficiently to operate the meter 56, which had previously been grounded through a high-resistance relay 124. The relay 156 also operates the cord meter 57. The circuit controlled by the relay 148 is broken after a short interval owing to this relay being disconnected by the self-locking relay 152. The meter 56 is so wound that the normal current is sufficient to keep its armature attracted. Release, Fig. 3. When the subscribers hang up, the relay 117 closes the circuit of lamp 127, and the relay 145 removes the shunt round the lamp 141. The withdrawal of the plug deenergizes the relay 130, which removes the holding ground G<13> from the switches C<3>, C<6>.